The prior art includes various systems designed to recover unpreassurized excess gas (i.e. “vent gas”) for re-injection or collection. In earlier gas processing systems, vent gas was either ignored, burned-off as a flare, or vented to the atmosphere away from the main processing system. Although these methods are relatively inexpensive, they have adverse environmental impacts and may create a safety hazard.
Some existing and prior-art systems use electrical power to vacuum vent gas from a low pressure or gas leakage area and pump the gas back into a host system. While these systems are effective, they require a source of electrical power and an electrical pumping mechanism, which could fail and/or create a safety hazard. Other systems have a separate dedicated mechanical compressor that scavenges, pressurizes and re-injects the vent gas back into the host system. Both of these types of systems are relatively complex and employ comparatively elaborate sensing and pumping mechanisms with multiple moving parts.
More recently gas recovery systems have been introduced that direct a relatively high pressure gas (known as “motive gas”) through a vacuum generating apparatus, such as a jet compressor, to create a vacuum. The vacuum is then used to suction the vent gas into the jet compressor. The suctioned gas is mixed with the motive gas to create a mixed gas stream, which is then injected back into the system. Although these systems do not require electrical or mechanical pumping mechanisms, they lack a simple and effective control system to maintain the various pressures and flow rates within predetermined limits and prevent the entry of air into the system.
The gas that is being processed preferably is recovered for the above reasons. Recovery of the gas requires that contamination be minimized, in order to preserve subsequent usability of the gas and also due to costs. Natural gas, for example, is priced based upon BTU value. Should the natural gas be contaminated during the recovery process with air, then the BTU value of the gas will be reduced and its value lowered. Other gases which are to be reacted, for example, should have minimal contamination in order to preserve reactivity.
The need exists for a self-contained gas recovery method and apparatus that has a reliable pressure regulating capability. The present invention provides a gas recovery system that includes a self-powered gas recovery device with no moving parts. The invention has a pressure regulation system that continuously monitors and adjusts a jet compressor inlet vent gas supply line pressure to ensure that the pressure in the vent gas supply line does not go below a pre-defined pressure, and thereby allow air gas to enter the system.